Java网络编程

Java网络编程

OSI 应用层、表示层、会话层、传输层、网络层、数据链路层、物理层
TCP/IP 应用层（HTTP,FTP,DNS..）、传输层(TCP,UDP..)、网络层(IP,ICMP)、数据链路层+物理层

通信三要素 一 IP和端口号，组合得网络套接字Socket(传输节点)

1、IP唯一标识Internet上计算机
2、JAVA中InetAddress类代表IP
3、IP分类，IPv4和IPv6 万维网 和局域网(192.168.0.0...192.168.255.255，本地地址127.0.0.1，localhost
4、端口号标识正在计算机上运行的进程，0~65535，公认端口 0~1023，注册端口 1024_{49151，动态私有端口49151}65535
5、TCP/IP 传输层 传输控制协议(TCP)和网络层 网络互联协议(IP)

//IP地址
InetAddress inet1 = InetAddress.getByName("127.0.0.0");
//域名
InetAddress inet2 = InetAddress.getByName("www.baidu.com");
//本地地址
InetAddress inet3 = InetAddress.getLocalHost();
//获得域名和地址
inet1.getHostName();
inet1.getHostAddress();

TCP和UDP

TCP
1、使用TCP协议，先建立TCP连接，形成数据通道
2、传输前，采用三次握手,点对点通信，是可靠的
3、TCP协议包括两个进程 客户端和服务端
4、连接中可以进行大数据量的传输
5、传输完毕，需释放已建立的连接，效率低

UDP
1、将数据，源，目的封装成数据包，不需要建立连接
2、每个数据报的大小限制在64k内
3、发送不管对方是否准备好，接受方不确认，不可靠
4、可以广播发送
5、发送数据后无需释放资源，开销小，速度快

案例1:TCP通信

public class C_S {

       

       @Test

       public void client() {

             Socket s1 = null;

             OutputStream os = null;

             try {

             InetAddress ip = InetAddress.getByName("127.0.0.1");

              s1= new Socket(ip,8899);

             

              os= s1.getOutputStream();

             os.write("你好，我是客户端".getBytes());

             }catch(Exception e) {

                    e.printStackTrace();

             }finally {

                    try {

                    os.close();

                    s1.close();

                    }catch(Exception e) {

                           e.printStackTrace();

                    }

             }

       

       }

       

       @Test

       public void server()  {

             ServerSocket ss = null;

             Socket s = null;

           InputStream is = null;

           ByteArrayOutputStream baos = null;

             try {

              ss= new ServerSocket(8899);

              s = ss.accept();

              is = s.getInputStream();

             

//           byte[] buffer = new byte[20];

//           <u>int</u> <u>len</u>;

//           while((<u>len</u> = is.read(buffer))!= -1) {

//                  String <u>str</u> = new String(buffer,0,<u>len</u>);

//                  System.out.println(<u>str</u>);

//           }

             baos = new ByteArrayOutputStream();

             byte[] buffer = new byte[5];

             int len;

             while((len = is.read(buffer))!= -1) {

                    baos.write(buffer,0,len);

             }

             System.out.println(baos.toString());

             System.out.println(s.getInetAddress().getHostAddress());

             }catch(Exception e) {

                    e.printStackTrace();

             }finally {

                    try {

             baos.close();

             is.close();

             s.close();

             ss.close();

                    }catch(Exception e) {

                           e.printStackTrace();

                    }

             }

       }

案例2:UDP通信

       @Test

       public void send() throws IOException {

             DatagramSocket socket = new DatagramSocket();

             

             String str = "UDP发送的数据";

             byte[] data = str.getBytes();

             InetAddress localHost = InetAddress.getLocalHost();

             DatagramPacket packet = new 
DatagramPacket(data,0,data.length,localHost,9000);

             

             socket.send(packet);

             

             socket.close();

             

       

       }

       

       @Test

       public void receive() throws IOException {

             DatagramSocket socket = new DatagramSocket(9000);

             byte[] buffer = new byte[100];

             DatagramPacket packet = new 
DatagramPacket(buffer,0,buffer.length);

             socket.receive(packet);

             

             System.out.println(new 
String(packet.getData(),0,packet.getLength()));

             socket.close();

            

       }

URL编程

URL 统一资源定位符,表示Internet上某一资源的地址 (种子)，代表服务器一个资源。
<传输协议>://<主机名>:<端口号>/<文件名>#片段名?参数列表

URL url = new URL("网址");
//public String getProtocol() 获取URL协议名
//public String getHost() 获取URL主机名
//public String getPort() 获取URL端口号
//public String getPath() 获取文件路径
//public String getFile() 获取URL文件名
//public String getQuery() 获取URL的查询名
//获取流
HttpURLConnection c =(HttpURLConnection) url.openConnection();
c.connect();
InputStream =c.getInputStream(0;